The present invention relates to a bath and method for the desizing and bleaching of fabrics in a single operation in a bath based on hydrogen peroxide.
Such a bath and method are the subject of French patent application No. 80 27866, equivalent to U.S. Pat. No. 4,457,760.
French patent application No. 80 27866 discloses using a bath comprising hydrogen peroxide, sodium hydroxide, a sequestering agent, an amylase, a surfactant, and, optionally, a stabilizing agent such as sodium silicate.
The commercial implementation of this procedure has encountered certain difficulties. On the one hand, the results obtained depend on the pH fixed at the start. In fact, at a very alkaline pH the bleaching is excellent, but the desizing generally is inadequate. Conversely, at a low alkaline pH the desizing is good but the bleaching is inadequate.
On the other hand, the level of results is closely linked to the nature of the fabric subjected to the desizing/bleaching treatment, with the enzymatic degradation of the starches used as sizing generating acidic products which cause the pH to fluctuate during the course of the reaction.
Depending on the quantity and the nature of the starches used for the sizing of the fabric, the pH of the desizing/bleaching bath is more or less modified during the course of the treatment, leading to important differences between the level of bleaching results and the level of desizing results.
These observations have led the applicant to search for a buffer capable of fixing the pH of the desizing/bleaching bath in order to have at one's disposal a simultaneous desizing/bleaching procedure, making it possible to obtain both optimum desizing and bleaching, while at the same time not adversely affecting the degree of polymerization of the particular fiber.